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Dexterous acoustic tweezers

Humans are dexterous in that we can perform a multitude of complex manipulation tasks with our hands. For an acoustic tweezer to be dexterous it must be able to grip and move micro particles or groups of particles independently and produce a variety of different particle distributions. The use of arrays of ultrasound sources allows a wide variety of acoustic pressure fields to be generated.

In this way a given device can be reconfigured to generate multiple and moveable field patterns: this leads to dexterous manipulation. However, this requires the solution of the following inverse problem: how to best excite the sources to achieve the desiredultrasonic field? And, equally importantly: how best to design a practical device to achieve this?

These recent developments build on work dating back to the 1950s and 60s in which the theory describing the acoustic radiation pressure on objects was first formulated. This theoretical framework continues to develop and now numerical models are close to being able to describe the interaction of high amplitude nonlinear waves with deformable particles such as cells.

This is important as many of the most exciting applications of acoustic tweezers are in biomedicine, where noncontact manipulation is particularly highly prized. Of the many possible applications dexterous acoustic tweezers, tissue engineering and the assembly of composite materials are discussed.